Corrugated packing for counterflow cooling towers



April 9, 1963 A. L KOHL ETAL CORRUGATED PACKING FOR COUNTERFLOW COOLINGTOWERS Filed April 21, 1960 il/Ill/lI/i BETA/U2 L. KOHL ELFQEQ LnFULLEQATTOQNEYS 3,984,918 CORRUGATED PACKING FOR COUNTERFLOW COOLING TOWERSArthur L. Kohl, Whittier, and Alfred L. Fuller, Fullerton,

Calif, assignors to The Fluor Corporation, Ltd, Los

Angeles, Calif., a corporation of California Filed Apr. 21, 1960, Ser.No. 23,722 1 Claim. (Cl. 261-112) This invention relates generally toimprovements in packing for cooling towers, and more specifically has todo with the provision of novel packing units to be assembled invertically spaced decks within cooling tower chambers, the unitsembodying corrugated grid sheets forming vertically open cells throughwhich air may flow upwardly in cooling relation with water being filmedand with minimum air pressure drop.

One of the problems overcome by the present invention consists in theexistence of an undesirably high pressure drop sustained by air flowingupwardly through conventional packing, the purpose of which is to filmliquid for cooling by the air stream. Thus, packing conventionally fillsthe bulk of the cooling tower chamber with uninterrupted verticalextent, and vertical openings through the packing are very small inorder to maximize the water film extent to promote cooling. However, itis found that when the vertical openings have maximum dimensions lessthan about /2 inch and particularly less than /4 inch, the water bridgesmany of the openings by surface tension action, thereby blocking theupward air flow through the openings and materially increasing thepressure drop sustained by that flow.

Accordingly, efforts have been made in the past to increase the rate ofair flow upwardly through the packing to prevent such surface tensionbridging of the packing cell openings, however, it has been found thatan undesirably high pressure drop is sustained by the flow so that on anover all basis the performance of the tower is limited.

According to the present invention, the pressure drop sustained by theair flowing upwardly through the packing is diminished substantiallywithout diminishing the amount of cooling of water flowing downwardly incounterflow relation to the air, all as compared with a conventionallypacked tower as described above, through the provision of verticallyspaced and horizontally extending decks of packing units in block form,each of these units having novel configuration to achieve the resultsdesired. .Each unit includes grid sheets extending in a face to faceseries of vertical planes for filming liquid to drain down the verticalsides of the sheets, at least some of the latterbeing corrugated, withface to face sheets being bonded together. Furthermore, the sheets formvertically open cells through which air circulates upwardly, the cellopenings being of suflicient size to prevent surface tension bridging ofliquid completely across the cell openings. I

In one form of the invention face to face adjacent sheets are corrugatedas will be described, whereas in another form certain of the sheets areflat and are interposed between the corrugated sheets. Water drainagefrom the cell openings is promoted by terminating the lower edges ofadjacent sheets at different elevations, it having been found that ifthe bottom edges of the cell forming sheets are all at the same level,water collects at these common level edges to reduce the free areaavailable for upward air flow, with concomitant increased pressure drop.

As mentioned above, the packing units extend in vertically spaced decks,which are to be distinguished from a vertically continuously packed zoneof equivalent size. In this connection it is believed that a majorportion of 3,'84,9l8 Patented Apr. 9, 1963 the cooling performanceincreases results from air turbulence in the open zone and where air andwater enter and leave the packing grids. Best performance is realizedwhen the vertical spacing between the grid decks is at the same order ofsize as the vertical dimension of each deck or packing unit, as will befurther discussed.

These and other objects and advantages of the invention, as well as thedetails of an illustrative embodiment, will be more fully understoodfrom the following detailed description of the drawings, in which:

FIG. 1 is a vertical elevation taken through a cooling tower chambershowing the vertically spaced decks of packing units; 7

FIG. 2 shows in perspective view the arrangement of verticallysuccessive packing units;

FIG. 3 is a side elevation illustrating the difference in height ofadjacent packing sheet lower edges;

FIG. 4 is a plan view of the FIG. 3 packing;

FIG. 5 is an elevation similar to FIG. 3 showing the manner in whichcorrugated and flat sheets are bonded together to have terminal loweredges at different heights;

FIG. 6 is a plan view of the FIG. 5 packing; and

FIG. 7 is a perspective view of a packing unit of somewhat diiferentconfiguration.

Referring first to FIG. 1, the cooling tower chamber 10 has side walls11 including louvers 12 through which air flows into the chamber lowerinterior space 13. ,The top of the chamber includes a venturi shapedstack 14 in which a fan 15 is driven by motor 16 so as to draw airupwardly from space 13 to discharge from the stack, the air flowing incounterflow relation to water moving down wardly within the towerchamber. The water may be conventionally distributed as by meansindicated at 17 including a header, laterals and nozzles distributingthe water in particles across the upper interior of the chamber.

Arranged in vertically spaced decks 18 within the tower are packingunits 19 each supported on cross-members 20 which may comprise thewooden beams as better illustrated in FIG. 2. The latter aretransversely spaced apart so as to support the edge portions of thepacking units 19, whereby the members 20 oifer minimal obstruction ofupward air flow from the tower. The block form packing units 19 arefurthermore arranged in, laterally continuous decks 18 so that all theair flowing upwardly and all the water flowing downwardly through thechamher must pass through the decks 18.

Referring now to FIGS. 2, 3 and 4, typical packing units 19 comprisegrid sheets 21 extending in a face to face series of vertical planes forfilming Water to drain down the vertical sides of the sheets, the latterbeing bonded together preferably at the locations shown at 22 in FIG. 4.Accordingly, the bonds extend vertically throughout the extents of thecorrugated sheets thereby providing a rigid block form structure havinggreat strength and capable of being fully supported only at the edges ofthe unit as indicated at 23 in FIG. 2.

In FIGS. 2 through 4, all of the grid sheets are corrugated as shown,the bonds 22 being located at adjacent corrugations. Also, face to faceadjacent corrugations have theirlower terminal edges 24 and 25 atdifferent elevations so as to prevent water collection at the lowerterminal edges before dropping from the grid. If these bottom edges areall at the same level, water collects at the common lower edge andaround the periphery of each cell 26 to reduce the free area availablefor air flow upwardly into the cell 26, thereby increasing the pressuredrop. By disrupting the bottom edge of the effective size of the cellfor air entry is kept as open as possible to minimize pressure drop. Forbest results, the difference in elevation between edges 24 and 25 shouldbe cona siderably less than the over all height of the packing unit 19,and also, such over all height is desirably considerably less than thehorizontal dimensions of the rectangular unit. In atypical example, asquare unit measuring 36 inches horizontally along each side has an overall height of 6 inches and the differences in elevation between thelower edges 24 and is between /8 inch and 4 inch.

In FIGS. 5 and 6, flat sheets 27 are interposed between pairs ofcorrugated sheets 28, the bonds 29 being located at the points Where thecorrugations meet the flat sheets i so that these bonds again extendvertically. Here again the differences in elevations between the loweredges 30 and 31 of the longer fiat sheets and interior corrugated sheetsare of the same size order in relation to the over all size of thepacking unit, as previously discussed in connection with FIGS. 3 and 4.Alternatively, in connection with FIGS. 5 and 6, the corrugated sheets31 can be longer than the fiat sheets 30 with the same desired resultsof preventing Water from collecting at the lower terminal edges.

An important feature of the invention consists 'in pro- 'viding cellopenings 26 in FIG. 4 and 32 in FIG. 6, of

sufficient size to prevent surface tension bridging of liquid completelyacross these openings. It has been found that the nominal diameter d ofthe openings as shown in FIGS. 4 and 6 should be between about /2 inchand 1 inch, these nominal diameters comprising the maximumcross-dimensions of the cell openings which generally are non-circular,as for example the heights of the corrugations. Furthermore, thesedimensions d are measured in the direction of series horizontal stackingof the sheets, as is clearly indicated. If the dimension a is less than/2 inch, Water begins to bridge the cell openingsto increasing extent asthe cell dimension d decreases. On the other hand, if the dimension d,is greater than 1 inch a serious loss in film surface area is sustainedwhich reduces the cooling performance. In addition, it has been foundthat blocking of the cell openings with scale or dirt does not occur ina cooling tower if the dimensions d are greater than 12 inch.

Another important feature of the invention is to limit the verticalspacing between the decks 18 in FIG. 1, to the same order dimension asthe vertical height of each deck. Thus, the vertical spacing between thedecks should be at least 3 inches, to promote efiective turbulence ofair in the open zones 35 between the decks, such turbulence increasingheat exchange or cooling of the water by air flowing through the decks.On the other hand, vertical spacing greater than about 1 foot or 12inches is of little use in improvingcooling performance throughpromotion of turbulenceand oth'e wise needlessly extends the columnheight.

Reference to FIG. 7 shows a somewhat modified square packing unitconsisting of flat sheets 36 interposed between corrugated sheets 37with bonds being provided at the locations 38 where-single corrugationsmeet the flat sheet-s.

This is distinguished from FIG. 6 wherein corrugations of sheets atopposite sides of ajflat sheet meet the latter at the general locationof the bond-29. Also, in FIG. 7 the bottom terminal edgesof the "flatsheets are notched as at 39 to'minimize water collection at these lowerterminal "edges. Here again the corrugated sheets 37' can'be notched incombination with or 4 separately from the flat sheets to give thedesired effect of minimizing water collection at the lower terminaledges.

The sheets themselves may comprise asbestos paper specially refined andsuitably treated to Withstand hot water flooded service, resinimpregnated asbestos paper, or resin bonded glass or polymeric fibercloth, these materials being preferred. Furthermore, the sheets maycontain very small perforations as indicatedat 40 in FIG. 7, permittingwater to migrate from one cell to another that is horizontally within apacking unit. Such perforations may for example be provided byincompletely impregnating glass fiber cloth with polyester resin.Generally speaking, the perforations will be sufficiently small thatwater will bridge them by'surface tension action, thereby promotingfilming of Water within the packing.

We claim:

In combination with a cooling tower for liquids comprising an uprighttower chamber having inlet and outlet openings for circulating airupwardly through said chamber in heat exchange relation with liquidmoving down- Wardly therein, the improvement which comprises verticallyspaced horizontally extending multiple decks of like packing units, theunits each having horizontally rectangular block form and being closelypacked horizontally across each deck, the spacing between verticallysuccessive decks being about 6 inches and approximately equal to thevertical dimension of each of said successive decks, each of saidunitsincluding grid sheets extending in a face to face series ofvertical planes for filming liquid to drain down the vertical sides ofsaid sheets, as least some of said sheets being corrugated and face toface sheets being bonded together, said sheetsforming Verticallystraight and open cells through which air circulates upwardly, the cellopenings having maximum cross dimensions between /2 and 1 inch, thesheet lower edges in each unit terminating at different verticalelevations the maximum dimensional difference of Which is substantiallyless than the overall height of the said unit, and means supporting saiddecks in vertically spaced relation, said means including cross membersextending horizontally under each deck and across the chamber interior,said members under each-deck having horizontal spacing to support alarge number of sheet lower terminal edges in each unit, the crossmember vertical dimensions being substantially less than the verticalspacing between successive decks and the cross member width dimensionsbeing substantially less than the horizontal overall dimensions of eachpacking unit.

References Cited in the file of this patent UNITED STATES PATENTS869,747 Starr Oct. 29, 1907 2,376,341 Burk et al.- May 22, 19452,793,017 Lake May 21, 1957 2,809,818 Munters Oct. 15, 1957 2,858,119Wright et al. Oct. 28, 1958 2,986,379 Kramig May 30, 1961 FOREIGNPATENTS 24,467 Great Britain Nov. 11, 1904 304,753 Great Britain Apr. 3,1930 657,550 Great Britain Sept. 19, 1951 678,100 Germany July 8, 1939846,092 Germany Aug. 7, 1952

